1. Field of the Invention
The invention relates to method and apparatus for driving a plasma display panel of a matrix display system.
2. Description of Related Art
AC discharge type plasma display panel is known as one of the plasma display panels (hereinafter, referred to as PDP) of the matrix display system.
The PDP of the AC discharge type has a plurality of column electrodes, and a plurality of row electrode pairs arranged via a discharge space filled with a discharge gas so as to cross each of the column electrodes. A discharge cell which emits light in red color, a discharge cell which emits light in green color, or a discharge cell which emits light in blue color is formed at each of intersecting positions of the row electrode pairs and the column electrodes embracing the discharge space, respectively.
Since each discharge cell performs the light emission by using a discharge phenomenon, it has only two states, xe2x80x9clight-on statexe2x80x9d in which the light is emitted at predetermined luminance and xe2x80x9clight-off statexe2x80x9d. That is, only the luminance of two gradations can be expressed. To realize a halftone luminance display corresponding to a supplied video signal by using the discharge cells, a gradation driving using a subfield method is performed.
According to the subfield method, a display period of time of one field is divided into N subfields, and a period of time during which the discharge cell is to be driven to continuously emit light (or turn off) is preliminarily allocated to each subfield. Each discharge cell is allowed to perform the light emission (or light-off) for each subfield in response to the input video signal only during the period of time allocated to the subfield. By a combination of the subfields for executing the light emission during one field display period of time, various halftone luminance at 2N (N:the number of subfields) stages (hereinafter, referred to as gradations) can be expressed.
When executing the gradation driving based on the subfield method, a driving apparatus (not shown) applies various driving pulses to the PDP, thereby causing various discharges in the discharge cells, respectively. That is, first, the driving apparatus applies reset pulses to the row electrode pairs of the PDP, thereby causing a reset discharge in all of the discharge cells. In this case, a predetermined amount of wall charges are uniformly formed in all of the discharge cells by the reset discharge. Subsequently, the driving apparatus sequentially allows the discharge cells to selectively perform an erasure discharge for each horizontal scanning line (hereinafter, referred to as one display line) in accordance with the input video signal. In this process, in the discharge cell in which the selective erasure discharge has been caused, the wall charges remaining in the discharge cell are extinguished, and the discharge cell is set to a xe2x80x9clight-off discharge cellxe2x80x9d. In the discharge cell in which the selective erasure discharge is not caused, since the wall charges formed by the reset discharge remain as they are, the discharge cell is set to a xe2x80x9clight-on discharge cellxe2x80x9d. Subsequently, the driving apparatus alternately applies sustaining pulses in a lump to all of the row electrode pairs the number of times corresponding to the subfields. In accordance with the application of the sustaining pulses, the discharge cells in which the wall charges remain, that is, only the discharge cells set to the xe2x80x9clight-on discharge cellsxe2x80x9d repetitively perform a sustain discharge only during the period of time corresponding to the subfields and maintain the light emitting state associated by the sustain discharge. In the discharge cells set to the xe2x80x9clight-off discharge cellsxe2x80x9d, a discharge is not caused, but the light-off state is maintained only during the period of time corresponding to the subfields.
In the PDP, however, since amounts of wall charges formed by the various discharges as mentioned above are not constant due to a temperature fluctuation of the panel, changes of the display luminance, time change, or the like, there is a problem that a variation occurs in intensity of the discharge and display quality deteriorates.
In a display apparatus using the subfield method, when a voltage of a scanning pulse is raised, an electric potential difference increases between the column electrodes and the row electrodes. In a pixel data writing step, the selective discharge easily occurs in the discharge cell which should become the light emitting cell by the application of a pixel data pulse of a low voltage. There is, however, a possibility that an erroneous discharge occurs in the discharge cell which should become the non-light emitting cell by the application of a pixel data pulse of a high voltage.
When the voltage of the scanning pulse is reduced, since the potential difference between the column electrodes and the row electrodes decreases, in the pixel data writing step, erroneous discharge does not occur in the discharge cell which should become the non-light emitting cell by the application of the pixel data pulse of the high voltage. However, the selective discharge becomes hard to occur in the discharge cell to which the pixel data pulse of the low voltage is applied.
The invention is made to solve the above problems and it is an object of the invention to provide a driving method of a plasma display panel which can always perform a image display in a preferable way.
It is, therefore, another object of the invention to provide a driving method of a plasma display panel which can perform a high quality image display by executing a proper selective discharge while preventing an erroneous discharge in a discharge cell in a pixel data writing step.
According to one aspect of the invention, there is provided a driving apparatus of a plasma display panel which has a plurality of row electrode pairs corresponding to display lines and a plurality of column electrodes arranged so as to cross each of the row electrode pairs and in which a discharge cell serving as a pixel is formed in each intersecting portion of the row electrode pairs and the column electrodes and which is driven every plural subfields constructing one field display period of time of a video signal, comprising: a resetting part for repetitively applying reset pulses to all of the row electrode pairs in at least one of the subfields and allowing all of the discharge cells to repetitively execute a reset-discharge, thereby initializing each of the discharge cells into either a light-on discharge cell state or a light-off discharge cell state; an addressing part for applying scanning pulses to one of each of the row electrode pairs in each of the subfields and applying pixel data pulses corresponding to the video signal to the column electrodes, thereby allowing each of the discharge cells to selectively discharge, and setting the discharge cells to either the light-on discharge cell state or the light-off discharge cell state; and a light emission sustaining part for applying sustaining pulses to each of the row electrode pairs in each of the subfields the number of times corresponding to the subfields, thereby allowing only the discharge cells in the light-on discharge cell state to repetitively execute a sustain-discharge, wherein a change rate of a voltage value in a trailing interval of the last sustaining pulse among the sustaining pulses is milder than that of a voltage value in a trailing interval of at least the sustaining pulse just before the last sustaining pulse.
According to another aspect of the invention, there is provided a driving apparatus of a plasma display panel which has a plurality of row electrode pairs corresponding to display lines and a plurality of column electrodes arranged so as to cross each of the row electrode pairs and in which a discharge cell serving as a pixel is formed in each intersecting portion of the row electrode pairs and the column electrodes and which is driven every plural subfields constructing one field display- period of time of a video signal, comprising: a resetting part for repetitively applying reset pulses to all of the row electrode pairs in at least one of the subfields and allowing all of the discharge cells to repetitively reset-discharge, thereby initializing each of the discharge cells into either a light-on discharge cell state or a light-off discharge cell state; an addressing part for applying scanning pulses to one of each of the row electrode pairs in each of the subfields and applying pixel data pulses corresponding to the video signal to the column electrodes, thereby allowing each of the discharge cells to selectively discharge, and setting the discharge cells to either the light-on discharge cell state or the light-off discharge cell state; and a light emission sustaining part for applying sustaining pulses to each of the row electrode pairs in each of the subfields the number of times corresponding to the subfields, thereby allowing only the discharge cells in the light-on discharge cell state to repetitively execute a sustain-discharge, wherein a change rate of a voltage value in a trailing interval of the last reset pulse among the reset pulses is milder than that of a voltage value in a trailing interval of at least the reset pulse just before the last reset pulse.
According to still another aspect of the invention, there is provided a driving method for a gradation driving of a plasma display panel in accordance with a video signal, the plasma display panel having a plurality of row electrode pairs having a capacitive load between the pairs and a plurality of column electrodes which are arranged so as to cross the row electrode pairs and form a discharge cell in each intersecting portion, wherein a display period of one field in the video signal is made up of a plurality of subfields, in each of the subfields, executed are: a pixel data writing step of forming pixel data indicative of either a light emitting cell or a non-light emitting cell with respect to each of the discharge cells of the plasma display panel in correspondence to the video signal, sequentially applying scanning pulses to one of each of the row electrode pairs, and applying pixel data pulses corresponding to the pixel data to the column electrodes synchronously with the scanning pulses, thereby setting each of the discharge cells into a state of either the light emitting cell or the non-light emitting cell; and a light emission sustaining step of alternately applying sustaining pulses to the plurality of row electrode pairs the number of times corresponding to a weight of each of the subfields so as to allow only the discharge cells which have been set into the state of the light emitting cell in the pixel data writing step to effect a sustain-discharge, and a trailing edge portion of the sustaining pulse which is applied finally among the sustaining pulses which are applied in the light emission sustaining step has an undershoot part below a ground potential.
According to a further aspect of the invention, there is provided a driving method for a gradation driving of a plasma display panel in accordance with a video signal, the plasma display panel having a plurality of row electrode pairs having a capacitive load between the pairs and a plurality of column electrodes which are arranged so as to cross the row electrode pairs and form a discharge cell in each intersecting portion, wherein a display period of one field in the video signal is made up of a plurality of subfields, in each of the subfields, executed are: a pixel data writing step of forming pixel data indicative of either a light emitting cell or a non-light emitting cell with respect to each of the discharge cells of the plasma display panel in correspondence to the video signal, sequentially applying scanning pulses to one of each of the row electrode pairs, and applying pixel data pulses corresponding to the pixel data to the column electrodes synchronously with the scanning pulses, thereby setting each of the discharge cells into a state of either the light emitting cell or the non-light emitting cell; a light emission sustaining step of alternately applying sustaining pulses to the plurality of row electrode pairs the number of times corresponding to a weight of each of the subfields so as to allow only the discharge cells which have been set into the state of the light emitting cell in the pixel data writing step to effect a sustain-discharge, in at least one of the plurality of subfields; and a resetting step of applying reset pulses to all of the row electrodes of the plurality of row electrode pairs prior to the pixel data writing step, allowing each of the entire discharge cells of the plasma display panel to reset-discharge, and initializing all of the discharge cells, and a trailing edge portion of the reset pulse which is applied finally among the reset pulses which are applied in the resetting step has undershoot part below a ground potential.